Author Topic: Single phase to three phase sinewave converter  (Read 10593 times)

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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #50 on: January 14, 2019, 09:25:59 pm »
Because you have not seen something, does not mean that it is not true. Especially if someone, who lives there (you do not and hardly to believe you ever did) for his whole life, has formal education and a degree in power electronics and is professionally qualified (although for not so long) to work on mains installations and appliances, should know better than you, how mains distribution and networks look here like?

And yes, I insist upon what I have said. The need for rotary phase converters is completely unheard of here. And also yes, the distribution of electric power and the general technical level of electrical installations in the US is way behind what is available and commonly used and done in the central EU (but it seems, it is also valid for Spain?).

Please accept that as a fact. No offense, just stating facts. You just seem offended, that I use stronger language, when calling out things with names. But please rest assured, that I do this regularly, independent of the topic. You may like it or not, but please do not try masking your nonexistent arguments behind me using a strong language to call things out.

The only rotary converters that has been in wide use in our country (and very likely all our neighbors) and some of them are still in use, are ward-leonard type of drive systems, which are mostly used for quite different tasks, than making 3ph from 1ph. 

Even IanB has told you, that central/east Europe uses 3ph as a standard, but you just seem to selectively ignore that.

Now I will ignore YOU because we have already made enough mess in this thread, and I am not willing to deal with people like you (who know everything and been everywhere) any longer.
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #51 on: January 14, 2019, 09:29:41 pm »
Sorry folks for late reply, I had fever.

Let me write down brief requirements. So We developed a device which does testing coils of diesel generator. While testing there is a point when generator have to be off due to certain requirements and to continue testing we need to feed 3 phase AC to the coils of generator. Attached is rough block diagram.

Problem is we dont have time to develop inverter which is controlled by micorcontroller. it will require alot of firmware development. Our best bet would be a SoC or IC which takes downgraded mains supply and generates 3 phase output which is synced with input mains.

Thank you for the image and sorry for the mess in this thread.

Could you please explain the process, in which you feed 3x220V into the generator coils? What is it supposed to do? I can't figure out which test would need a very weak (100mA?) threphase synced supply.

Do you test the control electronics with it (hence just the small current required)?
 

Offline sanwal209Topic starter

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Re: Single phase to three phase sinewave converter
« Reply #52 on: January 14, 2019, 09:47:18 pm »
We only want the control boards to think that there are voltages present on the coil. We only require small current for it.
 

Offline CatalinaWOW

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Re: Single phase to three phase sinewave converter
« Reply #53 on: January 14, 2019, 10:08:05 pm »
Wouldn't a small transformer do the job?
 

Offline sanwal209Topic starter

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Re: Single phase to three phase sinewave converter
« Reply #54 on: January 14, 2019, 10:09:11 pm »
Transformer how?
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #55 on: January 14, 2019, 10:10:07 pm »
So in fact you will not feed any coils, just the measurement circuit, then small current will suffice. I have just wanted to be sure I understand your intention correctly.

Do you know how clean (THD, upper harmonics) the signals should be? What is the limit, what is still usable for the test?

I think unfortunately, that the digital solution may still be the easiest one. There is not much code that is needed to make a threephase inverter bridge to produce the voltage and to sync it to any other signal.

However, I think you could probably still make it happen in good old analog fashion. I have remembered, that one of my friends have built some fully analog controlled VFDs, so I have asked him if he could share the schematic of the 3ph VCO, and sure enough, here it is!

There are four OTAs used (2x LM13700, still should be available) and the frequency is voltage controlled.

Use the VCO input together with a PLL, for example a 4046 to lock the frequency of this to the mains input.

The output amplitude at the RST terminals should be stable, due to the AGC (on the left).  The phase stability and accuracy is given by the timing capacitors - all must be the same in capacity and stable in temperature. (Use good quality foil types)

Then use three analog amplifiers, something like TDA2030 to drive three small step-up transformers, to up the voltage from those few volts up to the desired size.

I think this analog amplifier + step-up transformer solution will have the advantage of producing very clean outputs, and is probably good enough for some tens of watts of output.

I can't think of anything simpler than this.  It is just a couple of OTAs, the PLL and three power amplifiers, plus the three output transformers. (Just use backwards connected small mains transformers)







 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #56 on: January 14, 2019, 10:18:30 pm »
In principle, the circuit above is an oscillator with a three phasing RC filters, except that the R part is created by the OTA, which serves as  voltage controlled resistor.

Each RC circuit provides 60 degree of shift, 180 degree the whole loop (oscillates).  That's why there is the inverting amplifier to obtain the third phase,  which is 60 + 180 degree away, to make the third phase of 240 degree shift.
 

Offline sanwal209Topic starter

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Re: Single phase to three phase sinewave converter
« Reply #57 on: January 14, 2019, 10:23:02 pm »
Indeed its a good solution. I was thinking about another solution

Mains AC 220 -> 5V -> Buffer -> 120 Phase sifter -> 120 Phase shiftier ->  TDA2030 -> Step Up Transformer
                                              |                            |
                                              |                            |__  TDA2030-> Step Up Transformer
                                              |__TDA2030-> Step Up Transformer

It will be more simple and we dont need PLL right?
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #58 on: January 14, 2019, 10:26:36 pm »
I think crating 3x 120 degree shift is not that easy, as 3x 60. You will in the end need probably more active parts in the circuit, than in the diagram above.

Also your solution will provide incorrect phase outputs, if the mains frequency gets offset away from the nominal, where the phasing networks have been calculated. I think the solution with 3x 60 degree loop will be more robust and not frequency dependent (i.e. less phase error).  :-//

If you change your mind you want to test 50  or 60 Hz system, you won't need to change all phasing networks. The PLL will just lock at different frequency and the output phase relations will be still correct. :-+

I am not sure, why are you afraid of a PLL. I think PLL is easier to implement, than to wrestle three 120 degree phasing networks.

My solution IC count: 2x LM13700, 1x opamp, 1x 4046 (or other similar device), plus 3x some monolithic power amp. I don't think it is that bad.
« Last Edit: January 14, 2019, 10:31:49 pm by Yansi »
 

Offline sanwal209Topic starter

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Re: Single phase to three phase sinewave converter
« Reply #59 on: January 14, 2019, 10:36:19 pm »
I simulated in Tina, Have a look at the attached schematics and Waveforms.

 

Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #60 on: January 14, 2019, 10:42:29 pm »
Difference in detail.  Single phase distribution exists for local areas (like where I live currently), but unless you are really rural the distance to a 3 phase source is much less than 5 miles.  In my case it is about a half mile (one kilometer) to 3 phase power.  It still is not economical to bring that in.  Hence the market for VFD and other converter technologies.

I am sure that it is hard to generalize about this to entire regions or countries.  Lucky for you that you live where 3 phase is available.  Who knows whether the money spent on that has held back your economy in other ways?

It's my understanding, even if you have a 3ph drop nearby -- say you're neighboring a commercial property that has it -- they still want $10k's to come out and install new hardware, and that's assuming it's allowable at all for, say, zoning reasons? (which I have no idea if that's a thing, but maybe it's part of why).

So yeah, 3ph is really rare in the US.  Evidently it's rare in Spain too; I've only ever heard it's standard in the rest of Europe, as Yansi has said.  I've not visited and inspected their breaker panels myself, I've only seen pictures of them.  I don't doubt the veracity of everyone who lives there and says it is in fact available. :)

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Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #61 on: January 14, 2019, 10:44:32 pm »
I simulated in Tina, Have a look at the attached schematics and Waveforms.

Looks nice. :)

I don't suppose you can take a close look at the control and see what it's sensing?  If it doesn't matter what frequency or phase each of the inputs is, you don't need a phase shifter at all, just wire them up straightaways!

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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #62 on: January 14, 2019, 10:48:51 pm »
I would not consider this solution.

it is: 1) fixed frequency only 2) you need a lot of precision parts, or trimming respectively, to reach satisfactory level of phase balance. Don't forget precision foil caps are rare, and a typical resistor is 5 or 1%.

I think the solution with OTA providing correct phase at all frequencies without the need for tuning the phasing networks, is better. More bang for the buck. My solution just needs the caps to be the same value. It is likely easier to find three caps of the same value, than to find and select some specific value (or to trim the resistors in circuit).

You would need to align both allpass filter branches to obtain correct phase and amplitudes.  The three phasing RC 3x 60 degree are self-aligned, always at 60 degree each to make the 180 degree shift to start oscillation.

Or have I missed st.?



 

Offline IanB

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Re: Single phase to three phase sinewave converter
« Reply #63 on: January 14, 2019, 10:57:00 pm »
It's my understanding, even if you have a 3ph drop nearby -- say you're neighboring a commercial property that has it -- they still want $10k's to come out and install new hardware, and that's assuming it's allowable at all for, say, zoning reasons? (which I have no idea if that's a thing, but maybe it's part of why).

So yeah, 3ph is really rare in the US.  Evidently it's rare in Spain too; I've only ever heard it's standard in the rest of Europe, as Yansi has said.  I've not visited and inspected their breaker panels myself, I've only seen pictures of them.  I don't doubt the veracity of everyone who lives there and says it is in fact available. :)

In the UK there is also a question of danger. Three phase 415 V is considered to be somewhat more dangerous than the normal 240 V single phase supply. You tend to see signs like this wherever 415 V is present inside a panel:



This is (probably) not something believed to be compatible with a normal home.
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #64 on: January 14, 2019, 11:07:00 pm »
That is the leg-to-leg (phase-to-phase) voltage.

We have 400V leg-to-leg, and 230V (any)leg-to ground.  Nothing special really, for any extra warnings to be present.  (so for the British 240V, a 415 is the correct leg-to-leg voltage). That is just normal voltages one has to expect, when poking his fingers in switchboards.

The load from the house is split equally (at least in theory) across the three phases, as each phase-to-ground voltage is the standard 230V (+-10%).

Only the large power hungry appliances work with all three phases, to be able to see the phase-to-phase voltage.  (There are also exceptions, some appliances use just single 400V input and are connected in between two phases, typically some industrial power supply modules and for example some welders use 400V single phase input - although typiccaly having a three phase plug, but only two phases used as a single 400V).
« Last Edit: January 14, 2019, 11:13:59 pm by Yansi »
 

Offline MrAl

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Re: Single phase to three phase sinewave converter
« Reply #65 on: January 15, 2019, 12:51:44 pm »
I have already suggested using a suitable microcontroller plus a 3phase power stage.

BLDC controllers would not very likely suit, because BLDC is typically (but not always, mind you) driven by square wave.  Any smarter controllers than that will likely have numerous feedback loops and it'll become quickly a mess, to make it produce a static voltage in open-loop mode.

Hi,

Yeah it could get hairy.  Like using two and shifting the phase and AND'ing to get a pseudo sine.
 

Offline CatalinaWOW

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Re: Single phase to three phase sinewave converter
« Reply #66 on: January 15, 2019, 01:56:56 pm »
Wouldn't a small transformer do the job?

Perhaps a better way to ask the question is this.  You show the desired circuit powered by a current tap on one of the phases.  Why not do taps on the other two? 

This at least would provide all three phases properly synched.  Amplitude could be handled by designing the taps appropriately, in other words making it a three phase transformer.  Additional thought could make it incapable of supplying much more than your required current, though this last step would be a custom transformer and perhaps not the cost effective solution.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #67 on: January 15, 2019, 04:11:17 pm »
So yeah, 3ph is really rare in the US.  Evidently it's rare in Spain too;
No, do not get me wrong. It is not rare at all. I could get it "easily" in exchange for large wads of cash (if I had large wads of cash).

Let us rewind for a moment. The OP needs very low power three phase supply for some tests or experiments. Someone says he would not have to deal with such "garbage" if he were in Europe where pretty much all households have 3 phase supply.  I say that is not so except in the sense that pretty much all households own a Learjet. Yes, if you have the money you can get one but you do not have one now ready to go and you do not have three phase supply ready for me to come over and plug in my three phase motor.

If the OP was in Europe he would have to deal with the same "garbage". He would have to go to some small business or shop to find 3 phase power because it would be extremely unusual to find it in a random household.

Three phase supply is much more expensive and it makes no sense to supply three phase power to all households. It requires more wiring, more expensive and complicated meters, breakers, etc. It makes no economic sense and I just can't imagine why any country would do it.

Now, if I really want to get three phase supply I can get it easily but that does not mean I have it now.

I can call the power company, call an electrician, pay a few thousand euros to upgrade the wiring, meter, etc, then sign a contract with the electric company that will cost me quite a bit every month, and I will have three phases right there at my disposal. The thing is that nobody does it because it just does not make economic sense unless your consumption is upwards of, say, 20 or 25 KW. Then yes, it makes economic sense but if you need 3 phase 100W supply every now and then you are better off finding an electronic converter.

The restaurant around the corner has 3 phase supply because they need it. They pay separately for active and reactive power. I helped them install capacitors with the fluorescent ballasts because they were paying a lot in reactive power and they did not understand why. All these things are something a homeowner can get himself into if he wishes, it is mainly a matter of money.  But most people who have a three phase motor for some machinery find it advantageous to buy a variable frequency drive because it is much cheaper and simpler.

So I remain skeptical that any country in the world routinely installs and supplies three phase power to every household. I am not saying it is impossible; I am saying it makes no sense and I therefore believe it would not be done. Now, if someone asserts this is the way it is done in some country I expect it would be easy to provide some evidence (rather than insults). It should not be difficult to find some cites, some videos, some websites, showing how, indeed, most households in such country have three phase meters, three phase breakers, etc. So far I have seen no evidence of this. None whatsoever.  Extraordinary claims require extraordinary evidence. Where is it?

Maybe in South Kangeronia they supply three phases which rotate counterclockwise and the meters count backwards too and the utility company pays you for the energy you use.  It may be true but it is unlikely and I would need to see some corroborating evidence.
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Offline Zero999

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Re: Single phase to three phase sinewave converter
« Reply #68 on: January 15, 2019, 04:28:09 pm »
It's my understanding, even if you have a 3ph drop nearby -- say you're neighboring a commercial property that has it -- they still want $10k's to come out and install new hardware, and that's assuming it's allowable at all for, say, zoning reasons? (which I have no idea if that's a thing, but maybe it's part of why).

So yeah, 3ph is really rare in the US.  Evidently it's rare in Spain too; I've only ever heard it's standard in the rest of Europe, as Yansi has said.  I've not visited and inspected their breaker panels myself, I've only seen pictures of them.  I don't doubt the veracity of everyone who lives there and says it is in fact available. :)

In the UK there is also a question of danger. Three phase 415 V is considered to be somewhat more dangerous than the normal 240 V single phase supply. You tend to see signs like this wherever 415 V is present inside a panel:



This is (probably) not something believed to be compatible with a normal home.
3 phase isn't that much more dangerous than single phase, since the voltage relative to earth is exactly the same. It's unlikely someone will get a shock between two phases.

Yes, three phase is rare in the domestic setting in the UK, but I've heard that in some EU counties it's standard.
 

Offline Simon

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Re: Single phase to three phase sinewave converter
« Reply #69 on: January 15, 2019, 05:40:22 pm »
In Italy up to a few years ago 3KW was your limit with extra fees getting you a 4.5KW supply. i don't know if it is still like that.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #70 on: January 15, 2019, 06:22:06 pm »
It is interesting to know how many of the standards we have today are the product of evolution. You can pick any standard device and think it is badly designed. British plugs, NEMA, Schucko, all have their cons and maybe you can find something if their favor but they all emerged like that for their own reasons. One thing I do not like about Schucko is that it is not polarized but the Wikipedia explains why. I also don't quite like the Earth contact system.

At any rate, in Italy they used to have different rates for lighting (luce) and for motor power (forza) and they had different plugs. Of course one of the most common items was a plug converter which allowed using cheap electricity for lighting.  https://en.wikipedia.org/wiki/File:ForzaLuce1950.jpg

Even though I have never seen it personally it used to be the same in Spain and a carryover from all that is that, even though today they are connected to the same meter and pay the same rate, circuits are either for "lighting" (luz) or for "power" (fuerza) and those circuits have different requirements. Lighting does not require protective earth while power does. I find it stupid. And also, as a carryover from those old times a thingy which allows three plugs into one socket is called an "electric thief", just like in Italy. You can search Google images for -ladrĂ³n electricidad- (electricity thief) and see what I mean.

I have a theory that the design of the BS plug was so big so that it could be used as a boat anchor in an emergency. ;)
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Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #71 on: January 15, 2019, 06:34:10 pm »
Getting back to the OP, it would not be too difficult to design a three phase signal generator, even of variable frequency, followed by three linear audio amplifiers. I think this would be an interesting project.

This might practical up to, say,  50 or 60 W per channel. Once yo get into some real power the linear amps are going to be dissipating some real heat and a switching amp would make more sense. 

I can't see a real need for a low power three phase source but it would be an interesting project.
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Offline capt bullshot

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Re: Single phase to three phase sinewave converter
« Reply #72 on: January 15, 2019, 06:59:33 pm »

Let us rewind for a moment. The OP needs very low power three phase supply for some tests or experiments. Someone says he would not have to deal with such "garbage" if he were in Europe where pretty much all households have 3 phase supply.  I say that is not so except in the sense that pretty much all households own a Learjet. Yes, if you have the money you can get one but you do not have one now ready to go and you do not have three phase supply ready for me to come over and plug in my three phase motor.


I don't own a Learjet, but just because I don't have enough space to build the appropriate hangar on my property ;)

So this is the panel in the basement, and the three-phase outlet in the basement. There's another one in the garage. The cooker / oven in the kitchen has a three-phase feed. It's been there when I bought that house, so no excuses I might have installed that just because I've wanted that. Anyway, if I would walk (I won't do that) to a random neighbor and ask him to show me his / her panel, it would be a three-phase installation like mine. Mine's quite a modern one, with an additional (single phase) meter for the solar installation, but older ones look similar, often you find a mechanical (Ferraris wheel type) three-phase meter. Very old ones have a single phase meter, but a three-phase feed available at the panel, one just has to ask the utility to replace the meter. There's no single phase distribution here at all. Even in e.g. a two-room rented flat it's normal to have three phase power at the breaker panel with a three-phase meter installed.

Other countries have other standards, for sure.

Edit: added a random (images search found) picture of a typical (old style) household distribution line (four wires, three phase). You won't find these anymore since they buried the cables under the streets in large scale some ten years ago.
« Last Edit: January 15, 2019, 07:13:05 pm by capt bullshot »
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Offline MrAl

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Re: Single phase to three phase sinewave converter
« Reply #73 on: January 15, 2019, 07:01:54 pm »
Hello again,

Quick note...

Around this area we mostly see 3 phase power systems in industry.
Yeah i think anyone can get it but it will cost much more than a standard home bi phase service (USA).
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #74 on: January 15, 2019, 07:52:38 pm »
So this is the panel in the basement, and the three-phase outlet in the basement. There's another one in the garage. The cooker / oven in the kitchen has a three-phase feed. It's been there when I bought that house, so no excuses I might have installed that just because I've wanted that. Anyway, if I would walk (I won't do that) to a random neighbor and ask him to show me his / her panel, it would be a three-phase installation like mine. Mine's quite a modern one, with an additional (single phase) meter for the solar installation, but older ones look similar, often you find a mechanical (Ferraris wheel type) three-phase meter. Very old ones have a single phase meter, but a three-phase feed available at the panel, one just has to ask the utility to replace the meter. There's no single phase distribution here at all. Even in e.g. a two-room rented flat it's normal to have three phase power at the breaker panel with a three-phase meter installed.
OK, this is interesting. I can't see the photos well so I will just take your word for it. Is this general use in all of Germany? Even what used to be Eastern Germany? What is the amperage or power available at the panel? Is the range/stove water heater or other appliances three phase? It would be interesting because I have never seen three phase appliances sold here. Part of it is that we have very expensive electric rates and using gas or other fuel is cheaper.

I mean, if they wanted they could build every home here with the panel already prepared and wired for three phase but it saves a little money at building time and it means a lot more cost to retrofit. Like so many other things. I would like to have cat5 ethernet cable in every room but it would cost me a fortune now to install when it could have been done at new construction for very little.
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